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A body is in equilibrium when the vector sum of forces is zero. Resolving each force into x and y components and adding them gives the resultant; the force needed to restore equilibrium is equal in size and opposite in direction. This is the closing side of the force polygon, and it is how a three-rope junction is solved.
Component sums
Rx = sum F cos(theta); Ry = sum F sin(theta)
Equilibrant
F = sqrt(Rx^2 + Ry^2), acting 180 degrees from the resultant
For a point, yes. An extended body also needs zero net moment, or it will rotate while its centre of mass stays put.
Anticlockwise from the positive x axis, the standard mathematical convention.